With the Lucy mission, asteroids of the 'Jovian Trojans' family will be explored for the first time. These are planetoids that have accumulated at two points in front of and behind the gas giant, where the gravity of Jupiter and the Sun cancel each other out – referred to as Lagrange points. After launching on 16 October 2021, NASA's spacecraft will arrive at the L4 point along Jupiter’s orbit in 2027 and observe five Trojan asteroids in succession at close range until 2028, as anticipated in this artist's impression. After a return to the inner Solar System, Lucy will finally study a system of two binary asteroids at the L5 point in 2033.
Lucy is a NASA Discovery mission successfully launched on 16 October 2021. The mission will explore for the first time the regions of the Jupiter L4 and L5 libration points, home of the Jupiter Trojan population. Trojans are trapped in these regions by a 1:1 orbital resonance with Jupiter, and therefore represent a population that is dynamically stable and isolated from other small body populations.
Because they reside at 5.2 au from the Sun beyond the solar system snowline, Trojans are believed to have experienced very limited thermal evolution, and to retain considerable amounts of volatile materials. They are therefore considered relatively unprocessed, primitive objects that share many commonalities with comets. Despite this interest, the nature of these objects is not fully understood. Also, the mechanism that led to their capture still remains a mystery. The Lucy mission, thanks to an innovative mission design, will be able to perform a tour across the two Trojan clouds, during which it will carry out flybys of 5 objects (of which at least three are binary systems) and at least two main belt asteroid during the cruise phase - the first flyby being the main-belt asteroid (152830) Dinkinesh on Novembre 1, 2023. By studying the diversity of these objects Lucy holds promise for shedding light on fundamental questions about the origin of the solar system.
The DLR contributes to the mission with its participation in the activities of the Lucy Science Team. Our group has the lead in the fields of ground-based photometric observations of the target objects, generation of low-order shape models, determination of the rotation state of the targets, and digital shape model generation with stereophotogrammetric techniques. The DLR group also participates in the mission operations and planning, with the specific task of encounter modeling and evaluation, aimed at determining the best encounter strategy for the maximisation of the scientific return within the available resources.
During the pre-launch and the early cruise phase, our group has been performing a continuous photometric monitoring of all Lucy targets from our observing station in Calar Alto, Spain, in order to determine their pre-encounter rotation states, shape models and sizes to the best possible degree of accuracy. The results of such observations and models, which combined photometric and stellar occultation data, are published in Mottola et al. (2020) and Mottola et al. (2023) for three of Lucy’s targets. Results for further targets are being analysed and interpreted, and will be submitted shortly for publication.
In 2022 we also participated in the design and conduction of the observations of the DART impact onto the Dydimos-Dimorphos binary system. Lucy observations benefit from a unique observing geometry, and combined with the DART and ground-based observations will allow a thorough study of the post-impact evolution of the debris cloud. Our group works with the Lucy and DART Team to analyse these data.
Scientific Participation of the DLR Institute of Planetary Research
